Two-component mixes for the preparations of polyurethane resins are well known. As a matter of fact, in an elemental sense, the first polyurethane resins were made by mixing two components, which is to say, by reacting together a polyol as one component and a diisocyanate as the other. This concept has become greatly refined and elaborated on during the subsequent growth of the polyurethane resin industry, and various two-component mixes have been reported, where one component comprises a prepolymer of polyols and the other one or more diisocyanates, one or more of which may be in prepolymeric form. The individual components may be capped; that is, the polyols may be wholly or partially terminated by isocyanate groups, and the isocyanate reactant (in the other component) may be wholly or partially terminated by a polyol. Two-component mixes are described, for example, in U.S. Pat. Nos. 4,410,597 and 4,101,473 (these same two patents disclose our preferred catalyst combination of dibutyl tin dilaurate --"DBTDL"-- and triethylene diamine --"DABCO"--, as used in our Example 1; see below). U.S. Pat. No. 4,410,597 further discloses polyurethane coatings made with certain isocyanates and acrylic esters. Resistance to acids and warm water is claimed. Polyol mixtures are known, e.g., polyethylene glycol and trimethylolpropane, in U.S. Pat. No. 4,137,200, Example 1. That patent also discloses solvent-free two-component mixes. Such mixes are also mentioned in P U Paints and Coatings, H. Koch et al, Hanser Publishers, p. 525 (1985), which reference recommends two-component spray equipment in view of the resins' short pot life and high viscosity. Such equipment is available commercially and is useful in applying the resin of the present invention.
Polyurethane coatings are known for use in the auto industry; see UK Patent Application No. 2,147,910A, published May 22, 1985; and U.S. Pat. Nos. 4,554,188, 4,400,497 and 4,525,570.
TABLE I provides a summary check list of additional relevant U.S. patents, with an indication of their relevance. Some of these patents are discussed at more length below.
U.S. Pat. No. 4,225,696 --Colpitts et al-- makes an isocyanate-terminated prepolymer by reacting an isocyanate with a polyether diol: 1/40; 3/15. (Indicia are to column/line in the patent.) The isocyanate can be MDI (diphenylmethane 4,4'-diisocyanate) (2/68), the diol can be poly(oxypropylene) glycol (2/45). The prepolymer is cured with a diol, polyol or a mix (1/43). The polyol may be glycerine (2/53) and/or poly(oxypropylene) triol (2/55). Formulation IV (5/25) has 3 polyols plus MDI. (The MDI is actually a mix with unidentified "adducts".) DBTDL catalyst is used (4/29). (Resistance to thermal distortion is mentioned, but the reference is merely to body heat, i.e., a dental plate.)
In Colpitts' formulation (his Table, col. 5) the ratio of polyols/isocyanate, i.e., A/B, is always about 1.
U.S. Pat. No. 4,376,834 --Goldwasser et al-- makes a prepolymer with MDI (5/18) and a polyether polyol (6/33), with MW greater than 500 (6/15) and a functionality 2-4 (6/48). The prepolymer is reacted with a 3-polyol mix comprising a triol and a diol (6/49) and glycerol (8/30). See, e.g., Goldwasser's TABLE III. A/B in Example 1 is 0.62, in Examples 2 and 3, 0.54, and Example 4, 0.65. The other examples appear to give about the same or lower ratios. Example 9 describes humidity tests on a coating made with MDI, 1,4-butanediol, neopantyl glycol, and a polytetramethylene glycol. Substantial gains in weight and loss in Izod impact were reported.
Polyol mixes are not new, though our particular three in their particular proportions do indeed appear novel as Component A.
In addition to U.S. Pat. No. 4,225,696 to Colpitts and U.S. Pat. No. 4,376,834 to Goldwasser, other patents disclose 3-polyol mixes, e.g.:
U.S. Pat. No. 3,993,576 --Examples 15 and 16 show glycerine plus an adduct of glycerine with propylene oxide end-capped with ethylene oxide plus a solubilizer for the polyols, i.e., an adduct of an alkylene glycol with an alkylene oxide. In separate statements, the high-molecular weight polyols have hydroxy equivalent weights of 650-3,000 and 2-4 hydroxyl groups per molecule. Mixtures are included (1/30-36), including glycerine (1/43).
U.S. Pat. No. 4,131,604 uses a 3-polyol mix, but one of the polyols is required to be polytetramethylene ether glycol, which we do not have. Also, the diisocyanate must be aliphatic.